In the deprecation warnings for ++/-- on index types, emit a fixit hint to rewrite into

the correct call to .successor() or .predecessor().

This wraps up <rdar://problem/23708702> Emit deprecation warnings for ++/-- in Swift 2.2

Author: lattner

include/swift/Parse/Lexer.h

@@ -264,8 +264,9 @@ class Lexer {
   /// resides.
   ///
   /// \param SR The source range
-  static CharSourceRange getCharSourceRangeFromSourceRange(const SourceManager &SM,
-                                                           const SourceRange &SR) {
+  static CharSourceRange
+  getCharSourceRangeFromSourceRange(const SourceManager &SM,
+                                    const SourceRange &SR) {
     return CharSourceRange(SM, SR.Start, getLocForEndOfToken(SM, SR.End));
   }
 

lib/Sema/MiscDiagnostics.cpp

@@ -1113,19 +1113,30 @@ bool AvailabilityWalker::diagnoseIncDecDeprecation(const ValueDecl *D,
 
   // If the expression type is integer or floating point, then we can rewrite it
   // to "lvalue += 1".
-  if (isIntegerOrFloatingPointType(call->getType(), DC, TC)) {
-    const char *addition = isInc ? " += 1" : " -= 1";
-
+  std::string replacement;
+  if (isIntegerOrFloatingPointType(call->getType(), DC, TC))
+    replacement = isInc ? " += 1" : " -= 1";
+  else {
+    // Otherwise, it must be an index type.  Rewrite to:
+    // "lvalue = lvalue.successor()".
+    auto &SM = TC.Context.SourceMgr;
+    auto CSR = Lexer::getCharSourceRangeFromSourceRange(SM,
+                                         call->getArg()->getSourceRange());
+    replacement = " = " + SM.extractText(CSR).str();
+    replacement += isInc ? ".successor()" : ".predecessor()";
+  }
+  
+  if (!replacement.empty()) {
     // If we emit a deprecation diagnostic, produce a fixit hint as well.
     TC.diagnoseDeprecated(R, DC, Attr, D->getFullName(),
                           [&](InFlightDiagnostic &diag) {
       if (isa<PrefixUnaryExpr>(call)) {
         // Prefix: remove the ++ or --.
         diag.fixItRemove(call->getFn()->getSourceRange());
-        diag.fixItInsertAfter(call->getArg()->getEndLoc(), addition);
+        diag.fixItInsertAfter(call->getArg()->getEndLoc(), replacement);
       } else {
         // Postfix: replace the ++ or --.
-        diag.fixItReplace(call->getFn()->getSourceRange(), addition);
+        diag.fixItReplace(call->getFn()->getSourceRange(), replacement);
       }
     });
 

test/expr/expressions.swift

@@ -819,8 +819,10 @@ func swift22_deprecation_increment_decrement() {
   _ = f-- // expected-warning {{'--' is deprecated: it will be removed in Swift 3}}
 
 
-  ++si      // expected-warning {{'++' is deprecated: it will be removed in Swift 3}}
-  --si      // expected-warning {{'--' is deprecated: it will be removed in Swift 3}}
+  ++si      // expected-warning {{'++' is deprecated: it will be removed in Swift 3}} {{3-5=}} {{7-7= = si.successor()}}
+  --si      // expected-warning {{'--' is deprecated: it will be removed in Swift 3}} {{3-5=}} {{7-7= = si.predecessor()}}
+  si++      // expected-warning {{'++' is deprecated: it will be removed in Swift 3}} {{5-7= = si.successor()}}
+  si--      // expected-warning {{'--' is deprecated: it will be removed in Swift 3}} {{5-7= = si.predecessor()}}
   _ = --si  // expected-warning {{'--' is deprecated: it will be removed in Swift 3}}
 }